1. Field of the Invention
The present invention relates to an air intake apparatus for supplying an air to an engine, and in particular to an air intake apparatus enabling to suppress air suction noise. The present invention also relates to an air cleaner for filtering a sucked air to be led to an engine.
2. Description of the Related Art
A schematic view of the air intake apparatus is shown in FIG. 19. As seen in the same, the air intake apparatus 100 comprises an air intake duct 101, a resonator 110, an air cleaner 103, an air cleaner hose 104, a throttle body 105, and an intake manifold 106. In the intake apparatus 100, there occurs a problem about noises (called as “air suction noise” hereafter) getting out from an air intake port 102 of the intake duct 101.
FIG. 20 shows frequency distributions of suction noises without disposing the resonator 110 and a throttled part 111. As seen, the suction noise has plural resonance peaks. Of these plural resonance peaks, for example, a resonance peak A around 160 Hz is caused by a primary resonance mode of the intake duct 101. A peak B around 320 Hz is caused by a secondary resonance mode of the intake duct 101. A peak C around 260 Hz is caused by the primary resonance mode of the air cleaner hose 104. The resonance peaks above 150 Hz are caused by members respectively composing the intake apparatus 100. Accordingly, if changing length of paths of the respective members, the resonance peaks maybe comparatively easily adjusted. Therefore, the resonator 110 small in capacity may be adopted for lowering the resonance peaks existing in middle and high frequency ranges.
However, more noise reduction has been required over the whole range of the frequency of the noise to improve amenities of the inside of the car.
Further, a resonance peak D named as so-called low frequency heavy noise is not caused by each of members composing the intake apparatus 100. The resonance peak D is caused in the full length of the intake path 107 from the intake port 102 to the intake manifold 106. The intake apparatus 100 takes a pipe passage of one-side closed end where the intake port 102 is an opening end, while an intake valve (not shown) partitioning the intake manifold 106 and a combustion chamber 109 otherwise an upper face of a piston, are a closing end. Thus, the resonance peak D in the low frequency range is caused in the full length of the intake path 107. If the frequency of the resonance peak D agrees with an air pulsation transmitted from the side of the engine, the air suction noise radiated from the intake port 102 is made large. It is therefore difficult to lower the resonance peak D, that is, to suppress the low frequency heavy noise.
For suppressing the low frequency heavy noise, the intake duct 101 or the air cleaner 103 of the intake apparatus 100 is arranged with the resonator 110 of comparatively large capacity as around 2×10−3 to 10−2 m3.
There is often a case that a throttled part 111 is often arranged together with the resonator 110 of large capacity nearly the intake port 102 of the intake duct 101 for increasing acoustic mass and decreasing the air sucking noise.
But, as mentioned above, the resonator 110 for controlling the low frequency heavy noise is comparatively large in the capacity, and a whole of the intake apparatus 100 is made large accordingly, so that spaces for mounting other devices than the intake apparatus 100 are made narrow.
If the area of the intake path is throttled by the throttled part 111, an air flowrate to be supplied to the combustion chamber 109 decreases. In particular, when the engine rotates at high speed, a desired air flow rate is not effected, and an engine output goes down.